BIOLOGY
CHAPTER 5
1. Genotype and Phenotype
Genotype = information for all inherited traits of a certain organism
characteristics/features that are inherited, which cannot be changed
Phenotype = The appearance of an organism, can be changed
In every cell is nucleus
In every (human) nucleus (46) chromosomes
DNA = Deoxyribo Nucleic Acid
DNA = built up of four bases: guanine, cytosine, thymine, adenine
DNA = only built in combinations: C-G and A-T
2. Chromosomes and Genes
23 pairs, 46
chromosomes
Cell
nucleus
chromosome
genes
DNA
Cell has nucleus has chromosomes built up of genes built up of DNA
Genes can be on/off
e.g. in liver cells info for hair production is off
In body cell genes are in pairs
In sex cell genes are NOT in pairs
Two sex cells join nuclei join genes form pairs
Genotype of organism = decided at moment of fertilization
Cell division = cells (parent cells) dividing and forming new cells (daughter cells)
3. Sexual Reproduction
Sexual reproduction = the formation of a new individual following the fusion of two
sex cells
Sexual reproduction produces new genotypes in the offspring
Non-identical twins = two fertilized egg cells
Identical twins = one fertilized egg cell split in two identical cells
4. Mutations
Mutation = a change in one or more genes
Mutation = usually no consequences
Mutation in sex cell create offspring with mutation
Organism with mutation in phenotype = a mutant
Causes:
- Chemicals (asbestos, tobacco)
- Radiation (UV, x-rays, nuclear)
Mutation can result in accelerated cell division clump of cells = tuamour
If tumour spreads malignant tumour (= cancer)
Metastasis = other tumours in body due to a spread malignant tumour
5. The Theory of Evolution
Evolution = a change in a species over a long time period
Three things needed:
1. Long period of time
2. Change of environment
3. Change of DNA
Example:
organism is born with mutation environment favours organism with this mutation
more and more organisms have this mutation
the normal organism die out (natural selection)
New species = formed
because groups of one species are isolated
6. Evidence supporting the Theory of Evolution
- fossils
- remains of organisms (mostly imprint in rock
- most of the time only bones remain
- similar bone structure
- similar bone structure shows mammals have common ancestor
- rudimentary organs
- unnecessary bones
- supports fact that different organisms have one common ancestor
- similar embryonic development
- organisms look alike as embryos
- supports idea that organisms have one common ancestor
7. History of Life on Earth
Earth = 4.6 billion years old
First organisms = 3.8 billion years ago
8. Biotechnology
Biotechnology = techniques that use living organisms to produce useful substances
Genetic modification:
- get genes of organism 1 with a special trait (characteristic)
- put genes in organism 2, where you want the trait
- ^^ this is called recombinant DNA technique
Cloning:
- Artificial Embryo Twinning
embryo is split placed in surrogate animal (host mother) all babies
from embryos are genetically identical
- Somatic cell nuclear transfer (SCNT)
two good organisms reproduce egg cell is taken and divided into cells good
cells are fused with donor cells cell is placed in host mother animal
Crime prevention:
- DNA found at crime scene can be matched with suspects DNA
9. Genetic Testing
Some illnesses can be inherited
e.g. woman with breast cancer can pass this on to offspring
Genetic counsellor works out if offspring will have illness
Ultrasound scanning:
- machine sends out waves which detect abnormalities in foetus
Pregnancy Chorionic Villus Sampling (CVS):
- tissue taken from placenta containing cells formed by embryo are studied
- abnormalities in chromosomes can be detected
Amniocentesis
- amniotic fluid (containing cells from foetus) is taken from uterus
- chromosomes of cells are tested
!! with tests more risk of miscarriage
10. Sex Chromosomes
Female 23rd pair of chromosomes = xx
Male 23rd pair of chromosomes = xy
Egg cell = always x
Sperm cell = x or y
X
XX
XX
XY
XY
